The immediate reason for which artefacts are not substances is arrived at only by means of the consideration of matter as parts and the focus on the relation of parts and whole, which is undertaken in this chapter. Indeed, artefacts fail to satisfy the substantiality criterion, according to which no substance is composed of parts present in it in actuality (Met. Z 13). I show that Aristotle regards living beings as constituted of parts in potentiality, while he conceives of artefacts as constituted of parts present in actuality. Because their parts are in actuality, artefacts are not as unified as substances, but because artefacts still possess an inherent form, they cannot be downgraded to mere heaps. Thus, artefacts are hylomorphic compounds, but not substances at all.

In the Finale we examine to what extent Causal Mechanism can be seen as a descendant of the original notion of mechanism developed in seventeenth century, by examining possible extensions of the seventeenth-century notion of mechanism and discussing whether they can be used to characterise mechanism as a concept-in-use. We identify two conditions that a biological explanation has to satisfy in order to count as mechanistic, both of which were central in Old Mechanism: the condition of intelligibility and the condition of the priority of the parts over the whole. We use these two conditions to distinguish between two notions of mechanism: a more narrow one that incorporates both the intelligibility condition and the condition of the priority of the parts and a broader one that incorporates only the intelligibility condition and is thus a weakened form of mechanism. We claim that an account of mechanism as a concept-in-use requires the weakened notion, which when viewed in terms of Causal Mechanism has nevertheless enough content so that it can be seen as a descendant of the original concept.